Process of making potassium aluminum fluoride



Patented Dec. 5, 1933 rnocnss or MAKING POTASSIUM ALUMIN UM FLUORIDE V Arthur- H. 'Henninger, St. Albans, N. Y., assignor to General Chemical Company, New York, N, Y., a corporation of New York no Drawing. Application June 18, 1931 Serial No. 545,369

This invention relates to potassium aluminum fluoride and methods of making the same and particularly to methods of producing potassiumv aluminum fluoride in a form suitable for use as an insecticide. It has heretofore been proposed to use potassium aluminum fluoride as an insecticide for the control of various insect pests. This material is considered to possess advantages over lead 0-arsenate as aninsecticide for ;the reason that;

-been-produced by adding a'solution of potassium carbonate-to a solution of aluminum sulfate and thereafter adding hydrofluoric acid to themixed.

solutions". The reactionsf'which take place in the process heretofore proposed, may be expressed by the following equation:

It will be noted from this equation that the re- 26gaction results in the formation of potassium sulfate which largely remains in the mother liquor from which the potassium-aluminum-fluoride is precipitated, thus representing a substantial loss in the process. Furthermore, the precipitate 30fformed must be washed several times to reduce the amount of potassium sulfate in the precipitated product. The loss of potassium in the reactions and the time and expense required to purify the precipitate add to the cost of the product obtained.

I have discovered that the foregoing objections to methods heretofore employed can be overcome and potassium-aluminum-fluoride admirably suited for use as an insecticide can be produced -by reacting a solution of aluminum oxide (preferably in the hydrated form) in potassium hydroxide with an acid containing fluorine, the reacting materials being in such proportions that substantially all of the potassium is formed -into potassium-aluminum-fluoride. The reaction products consist substantially. solely of the complex fluoride and water.

Among the objects of my invention are to pro- 7 vide an improved process for producing potas- -sium-aluminum-fluoride, to obviate the losses in the reacting constituents heretofore involved in the production of said material and to produce potassium-aluminum-fluoride of such quality that it may be used as an insecticide.

.55 j These and other objects and features of my invention will appearfrom the following description thereof.

In practicing my invention I prefer to use hydrated aluminum oxide (AlzO3-3H2O') as the aluminum bearing compound and digest this ma-' co terial in a solution of potassium hydroxide. The digestion product which contains potassium aluminate'and an excess of potassium hydroxide is then treated with an acid containing fluorine such as hydrofluoric acid. The resulting reaction produces a precipitate of potassium-aluminumfluoride which maybe given a single wash with watc -dried by evaporation or otherwise and pulverized, if desired. The resulting product is very finely divided rendering it well suited for use as an insecticide.

The following example is illustrative of the foregoing procedure: i

4.08 parts by weight of' hydrated aluminum oxide (65.35% A1203) are boiled in a solution containing 9.32 parts of potassium hydroxide (79.4% K20) and 41.5 parts by weight of water. The boiling is continued for 30 minutes, using livesteam. 10.1 parts by weight of hydrofluoric acidlanalyzing 62.33% available HF) are then- 801 gradually added to the heated solution over a period of 25 minutes. The heat of the reaction keeps the liquor boiling and agitating during the addition of the hydrofluoric acid and after all of the acid is added, the mixture is boiled for about 20 minutes longer using live steam. The resulting precipitate is then filtered off, the produ'ct obtained is washed once with water, dried and pulverized. On analysis the product is found to contain' 98.8% KsAlFe, the remainder 90.: being impurities such as A1203, F8203 and silica. When given a screen test, 99.55% of the product passes through a 200 mesh screen.

In the foregoing example the proportions of the materials employed are substantially in the ratio of 1 molecular equivalent of hydrated aluminum oxide to about 6 molecular equivalents of potassium hydroxide and 12 molecular equivalents of hydrofluoric acid. The reaction which takes place in carrying out my process as de 10 scribed above may be represented by the equation: I

sium aluminum fluoride and water. Thus none a of the potassium or other valuable constituents are lost in the process and the resulting product is not contaminated by impurities resulting from side reactions.

5 I have used hydrofluoric acid containing a substantial amount of hydrofluosilicic acid in carrying out my process. It will also be apparent that I may if desired, dissolve potassium aluminate in water and react the solution of the potassium aluminate directly with potassium hydroxide and hydrofluoric acid. While I have referred to hydrated aluminum oxide as the aluminum bearing material employed, I may use bauxite for example as a source of hydrated aluminum oxide if desired. These and other modifications of my invention will be apparent to those skilled in the art, and may be employed without departing from my invention. It will also beunderstood that my invention is not limited to the use of the specific concentrations of the materials cited in the foregoing example since other suitable concentrations of the reacting materials may be employed, the process as described in the example being merely illustrative of the prea ferred form thereof.

I claim: V

, 1. A process for producing KaAlFc, which comprises the steps of dissolving aluminum oxide in a solution of potassium hydroxide and adding 0 hydrofluoric acid to the solution produced.

2. A process for producing potassium-aluminum-fluoride comprising the steps of boiling aluminumoxide in a solution of potassium hydroxide and thereafter adding hydrofluoric acid.

51. 3. A process for producing KaAlFs comprising the step of digesting a solution of potassium hydroxide containing aluminum oxide with bydrofluoric acid.

4, A process for producing potassium-alumi- 491? num-fluoride which comprises dissolving aluminum oxide in a solution of potassium hydroxide, heating the solution produced, and gradually adding hydrofluoric acid to said solution while said solution is heated. 1

5. A process of producing dry powdered potassium-aluminum-fiuoride in a form suitable for use as an insecticide which comprises boiling aluminum oxide in a solution of potassium hydroxide, and thereafter adding hydrofluoric acid to the resulting solution, separating the precipitate of potassium-aluminum-fluoride produced, washing the precipitate with water and then drying and pulverizing the precipitate.

6. A process of producing dry powdered KsAlF in a form suitable for use as an insecticide which comprises digesting a solution of potassium hydroxide containing 1 molecular equivalent of aluminum oxide to 6 molecular equivalents of potassium hydroxide with 12 molecular equivalents of hydrofluoric acid, evaporating the water contained in the resulting product and pulverizing the product. V V

7. A process of producing dry powdered potassium-a1uminum-fluoride in a formsuitable for use as an insecticide which comprises boiling approximately 1 molecular equivalent of aluminum oxide with about 6 molecular equivalents of potassium hydroxide in water until a sub-' stantial portion of the aluminum oxide is dissolved, gradually adding approximately 12 molecular equivalents of hydrofluoric acid'to the solution produced, while said solution is heated, separating the precipitate of potassium aluminum fluoride produced, washing the precipitate with water and then dryingand pulverizing the -precipitate.

ARTHUR H. HENNINGER.

(Certificate 0r Correction Patent No. 1,937,956. December 5,1933.

ARTHUR H. HENNINGER It is hereby certified that errors appear in the ginted specification of the above numbered patent requiring corrections as follows: age 1 line 90, for 98.8% read 98.28%; page 2, line 91, claim 6, for K AIF read If A12 and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Otifice.

Signed and sealed this 16th day of January, A. D. 1934.

Sm r. M. HOPKINS,

1 Acting Commissioner of Patents. 

